The present invention relates to disk apparatuses. More specifically, it relates to the arrangement of the each of units constituting a magnetic disk apparatus used as, e.g., an external storage for a computer, and a structure for cooling these units.
Magnetic disk apparatuses which have recently come into use are generally arranged in such a manner that, in order to attain a large capacity, each apparatus is constructed as an aggregate-type magnetic disk apparatus in which a plurality of head-disk assemblies (hereinafter abbreviated to "HDAs") are accommodated in one casing.
Apparatuses of this type include, for example, the apparatus known from "Nippon Telegraph and Telephone Public Corporation, Report on Researches and Ways of Application" (pages 313 to 315, Vol. 31, No. 1, 1982) in which, eight HDAs (referred to as disk enclosures (DEs) in this document) are mounted within one casing. According to this document, also mounted in the casing are four electronic circuit sections each capable of simultaneously controlling two HDAs, and four power sources each corresponding to one of the electronic circuit sections.
When the apparatus is observed from the functional viewpoint, two HDAs, one electronic circuit section for controlling these HDAs, and one power source together constitute one unit. On the whole, therefore, four sets, each set comprising one unit, are mounted in the casing. The inside of the casing is provided with four shelves on which the units are disposed one by one.
This arrangement of the conventional apparatus calls for a certain wiring arrangement. That is, lines must be extended horizontally to allow electrical connection from the power sources to the corresponding electronic circuit sections, and from these electronic circuit sections to the associated HDAs. Furthermore, interface cables extending vertically from a host apparatus (string controller) must be connected to each of the electronic circuit sections.
Various devices of the apparatus, such as the power sources, are cooled by air. Because power sources normally require cooling fans to be provided in correspondence therewith, it is assumed that each of the four power sources is provided with a corresponding fan and is cooled thereby, and that each of the four electronic circuit sections is also cooled by one cooling fan. All of the eight HDAs are cooled by air caused to flow by a fan from the lower portion to the upper portion of the casing. In addition, a plurality of fans are provided on the upper portion of the casing so as to discharge the air heated within the casing.
Each HDA accommodates therein a magnetic head for writing information thereon and reading information therefrom. In this connection, it is particularly desired that the magnetic head should be positioned on the associated magnetic disk medium with only a very small deviation involved. If the HDA is cooled to an inadequate extent, this results in an increase in the temperature of the HDA, thereby leading to an increase in the deviation in positioning the magnetic head due to the thermal expansion of various component parts of the HDA. Therefore, it is of importance that HDAs be cooled as adequately as possible and that any rise in the temperature of the HDAs be prevented. With respect to the electronic circuit sections, it is of importance that they be cooled adequately so that none of the allowable temperature ranges of their various circuit elements are exceeded.
With the above-described prior art, since each of the power sources and the electronic circuit sections is provided as enclosed within its own box, it is necessary to provide at least one cooling fan in correspondence with each of these devices. The entire apparatus therefore requires a large number of fans to be provided, thereby inevitably complicating the cooling system within the casing.
Furthermore, the arrangement of the conventional apparatus is such that a plurality of units, each comprising one power source, one electronic circuit section, and two HDAs, are independently disposed within the casing, while horizontally extending cables allow in-unit electrical connections and interface cables vertically extend from a host apparatus to each of the electronic circuit sections. Thus, the apparatus has a complicated wiring arrangement with various lines extending criss-cross, thereby often resulting in the occurrence of errors during maintenance operations for the devices within the casing, and an increase in the period of time required for these maintenance operations.